Is there a way to set the default float presentation for Python "{:5.3e}".format(a) if a=None and is not a float?

Question

Is there an easy way to set the default float presentation for Python's format command:

"{:5.3e}".format(a) 

so that if the variable a has a value of None instead of a float, some default like 5 spaces might be printed?

The format string can be include many fields and is given by a user. The values in a are calculated internally.

Answer 1

我会建议像

这样的东西

print("{:.3e}".format(a)) if a else print(" "*5).

您不需要5.3e，因为在科学记数法中，由于.3e，您总是得到5位数。除非您想将整个文本向右移动。然后你可以使用{:>10.3e}。